Recording by means of electric charges



Oct. 18, 1960 H. EPSTEIN 2,956,352

RECORDING BY MEANS OF mzcmc CHARGES Original Filed Nov. 14. 1952 CODE SELECTOR INVENTOR H ERM AN EPSTEIN W Kw AGENT RECORDING BY MEANS OF ELECTRIC CHARGES Divided and this application Jan. 24, 1956, Ser. No. 561,023

8 Claims. (Cl. 346-74) This is a division of my application for patent Serial No. 320,592, filed November 14, 1952, now Patent No. 2,9l9,- 170, entitled Means for Electrostatically Recording Signals.

This invention relates to methods and apparatus for recording patterns upon dielectric materials, and more particularly for electrically recording intelligible messages upon a record surface.

In radio communication or other electronic systems such as computers, the medium for recording commands or other intelligence in many cases comprises a coded tape. In general, the operational speed of the equipment is limited by the speed of such recording means. Accordingly, a high speed system is desired for recording purposes.

Speed has been limited in moving tape systems by mechanical transfer methods, since it has, in the past, been impractical to transfer the intelligence to a moving tape and accordingly the tape has been brought to a complete stop during its travel through a recording device, in many prior art systems. Not only does this action per se take more time to transfer a given message to a tape, but the mechanical design of the machine must take into account the relative changes of tape speed and accordingly provide more massive components. Accordingly, the system in ertia is increased, and this further limits the speed of the recording system. These disadvantages are overcome according to the present invention by avoiding mechanical information transfer systems, as Well as start-stop drive mechanisms.

Another consideration is that for a recording system to have wide application, it should be compatible with commonly used electronic coding and signaling systems. The record made should be distinct and permanent and a favorable signal-to-noise ratio should be attainable in reproducing the recorded intelligence. Liquid ink is often used as the recording agent, but this has the disadvantage of being subject to smudging. More acceptable records may be made when dry pigment powders are utilized, instead.

The present invention provides a recording system for impressing a pattern of electrostatic charges upon a movable dielectric body, such as a record tape, and for rendering the charged areas visible by applying pigmented power thereto as a spray or cloud. A permanent fixing process, such as spraying with a binder or heating to take advantage of thermoplastic properties, is used to hold the pigment in place and produce a permanent record. In one method of establishing the charged areas on the recording medium radiation from a radioactive or like source of charged particles is made use of, this radiation being directed and controlled to impinge upon the medium in suitable manner to produce the desired pattern of charges.

It is, accordingly, a general object of the invention to provide an improved method of and means for recording intelligible signals.

Another object is to provide low inertia, high speed recording apparatus.

Another object is to provide a method of and means for Patented Oct. 318, 196i) ice initially recording information as a pattern of electrostatic charges and later rendering said pattern visible as a permanent recordv Another object is to provide means of the above character for electrostatically recording information wherein said charges are derived from a stream of electrically charged particles.

A further object is to provide an electrostatic recording system of the foregoing character utilizing radiation from radioactive material as a source of charged particles.

Other objects and advantages of the invention will be apparent upon consideration of the following specification taken in conjunction with the accompanying drawings in which:

Fig. l is a diagrammatic representation of one form of a recording system embodying the principles of the in vention;

Fig. 2 is a schematic illustration of one phase of operation of the invention, comprising an inking process; and

Fig. 3 is a modification of the recording system of Fig. 1, illustrating further features which may be utilized in accordance with the teaching of the present invention.

A record medium which may be utilized in practicing the invention comprises a movable dielectric tape 12, shown in Figs. 1 and 3. The tape is adapted for high speed operation in conjunction with a suitable electronic code selector circuit 14 (Fig. 1) which controls the establishments of a charge pattern upon the tape in accordance with the intelligence to be recorded. Tape 12 is advanced by suitable tape feeding means comprising continuously rotatable rollers driven to advance the tape in the direction indicated by the arrows in Fig. 1. In the embodiment of this figure, the recorded charge pattern comprises code groups impressed upon the tape by pintype printing electrodes 1619, to which the potential of a grounded high voltage source 13 is selectively directed by signal-responsive electronic code selector circuit 14. An electrostatic field is thereby set up between the energized pin electrode or electrodes and a grounded base electrode 15. The dotted areas 21, etc. represent charges stored in or upon the surface layer of the dielectric tape 12 according to a pattern established by the recording means. The excitation of electrodes 16-19 is controlled in accordance with time sequences suitable to build up selected configurations, for example a series of characters, on the moving tape.

The illustrated, generally circular, form of the dots 21 which make up the latent electrostatic image pattern is characteristic of the use of cylindrical electrodes, exemplified by pin electrodes 16l9, and the dots may be considered to be the projections on the surface of the tape 12 of the end surfaces of these electrodes. In Fig. l the arrangement of these charged areas or dots 21, while not forming specific characters, illustrates the result of the above-referred-to selective excitation of pin electrodes 1619 at different times and in different groupings as the tape is continuously advanced past the row of electrodes.

Should the tape not have the proper dielectric charac teristic or surface resistivity for recording in the above manner, it may be passed through a bath of suitable coating material 23. This bath may comprise a thermoplastic resin, adapted to impart the desired properties to the tape, for example, polystyrene in a 10% benzene solution by weight, or other substance which is adapted to cause the tape to attain a surface resistivity of the order of 10 ohms per centimeter. The specific value of this resistivity is chosen according to the length of time the electrostatic latent image is to be stored on the tape be fore the application of pigment powder thereto to develop the image. Sui able heated drying rollers 25 and 26 may be provided intermediate the coating bath and the recording means, if necessary. Code selector 14 serves to commutate a high voltage derived from source 13 in such a way as to establish the desired pattern of charged areas upon the treated surface of the tape and determines the polarity of the charged areas, the efiect of polarity being referred to hereinafter in connection with Fig. 2.

Finely divided uncharged particles having a low mass if brought in contact with the treated surface of tape 12 will adhere to charged areas thereof. Accordingly, by subjecting the charged tape to a cloud 27 of finely di vided particles of suitably pigmented material supplied from reservoir 33 by means such as the blower 3t} and jet 31, the latent image comprising charged areas 21 is rendered visible as the pattern comprising pigmented dots 35. Since the initial adherence of the pigment particles in the charged areas is insufficient for permanent record purposes it is desirable to subject the record to a fixing process to permanently hold the particles in position. One such process includes spraying or otherwise coating the tape with an acrylic lacquer or a like clear liquid binder 38 by way of jet 39, to produce a permanent recrd at a portion 4% of the tape which has passed the jet.

In the visible display comprising the assembly of dots 35, each dot corresponds to the excitation by a single signal impulse of a particular one of the group of pin electrodes 16-19. Because of the relatively small cross section of the pin electrodes, the charged areas resulting therefrom, regardless of their contours, may be considered to be dots or points.

It will be apparent that the above described method of recording intelligence ofiers many advantages in a high speed system. For example, code selector 14 because of its inherent speed of operation readily impresses well-defined charged areas on tape 12 even during continuous motion of the tape at high velocity. Also, because all mechanical code selection devices are eliminated, the inertia of the recording system of the invention is negligible. The surface of the record medium bears a permanent indication of the recorded information and the use of dry pigment powder to render the latent electrostatic image visible eliminates any smearing such as may occur where liquid ink is used to make a record. In addition, high signal-to-noise ratios can be attained with a system such as has been described because of the contrast between the charged and uncharged areas.

Further improvement in the signal-to-noise ratio may be attained by processing the pigment powder in accordance with a phase of the invention illustrated by Fig. 2. It is found that, due to various slight attractive forces, some pigment particles may adhere to the surface of the recording medium where no charge has been established and thus prevent the signal-to-noise ratio in the record reaching a value as high as would otherwise be possible. By mixing a powdered substance such as corn meal 43 or sand 45 with the pigment particles 47 (Fig. 2) and turbulently agitating the mixture, as by jet 31, the rubbing together of the different substances will cause the particles thereof to receive charges in accordance with the relative positions of the substances in the triboelectric series. Thus, cream of tartar particles when agitated with corn meal will attain a negative charge whereas lycopodium powder agitated with sand will attain a positive charge. The ingredients preferably used in accordance with the presently described phase of the invention are selected to obtain a charge on the particles of the pigmented inking or developing substance which is of opposite polarity to that established in the charged areas of the record surface so that these areas will more firmly attract the inking particles. In this manner the ratio of the attractive force on the inking particles at the charged areas to the forces at the uncharged areas is increased. Because of the polarity of the charge on the sand or corn meal and the greater mass of the particles in comparison with the inking particles, these substances will not tend to become affixed to the charged areas of the tape.

As indicated in Fig. 3, instead of being the result of the application of a difference of potential to spaced electrodes, the record charges may be established on tape 12 by bombardment of ionic particles moving in a stream as. The ionic particles may be generated from the discharge about a body of radioactive material 51 and focussed into a stream by the electrostatically charged container 53 electrically biased by battery 52. An electrostatic control means 54, shown in the form of a grid electrode, is interposed in the path of the ions within the container to control the stream and when suitable potentiars are supplied thereto by control circuit 14 this grid is efiective to regulate the issuance of the stream from orifice 56, thereby selectively to control the pattern of charges received by recording medium 31.2.

Thus, assuming for purposes of illustration thatcontainer 53 is held at a'suitable constant negative potential, at the instant when grid 54 acquires a correspondingly suitable positive potential through excitation by circuit 14, a stream of negative ions issues from orifice 56 as the combined result of their repulsion by the charged container and their acceleration by the grid. This stream strikes recording medium 12 to form a charged area on the surface of the medium. With a suitably short period of positive excitation of grid 54, this area can be caused to have the form of a dot which upon later development appears as an elemental dot of the permanent record. The action thus corresponds to the recording of a dot by the excitation of one of the electrodes l6-19 of Fig. l. The number and positioning of particles 51 (with associated containers or other focusing means) employed in the arrangement of Fig. 3, as well as the sequences in which streams of charged particles emanating therefrom are permitted to reach the moving recording medium, determine the pattern of dots recorded, just as does the number of electrodes 16-19 and the sequences of their excitation in the arrangement of Fig. 1.

There is some evidence that in the last described mode of operation the ionic particles actually become imbedded in the dielectric recording material, to establish the charged areas of the record. The same also appears to be true when the electrode means of Fig. 1 is employed if the potentials and electrode spacing are chosen so that the electrostatic stress is sufiicient to ionize air particles between the electrodes and the tape and provide the necessary force to cause penetration.

According to the arrangement of Fig. 3, the charged areas of the tape are subjected to a cloud of inking or pigment particles 27, produced in an alternate manner to that illustrated in Fig. 1 by a revolving brush 55 turbulently mixing the pigment powder 34 and throwing it against the charged face of tape i2. Gravity forces the more massive elements to fall away from the tape, as particularly referred to in connection with the triboelectn'c mixtures of Fig. 2, leaving a deposit of pigment particles only. If either the pigment particles are of a waxy or like thermoplastic nature or recording medium 12 is supplied with a thermoplastic coating, as previously described, heat treatment of the medium, as at position 58, can be made use of to permanently attach the adhering pigment powder to the record surface or cause it to penetrate below the surface.

As will be apparent, various features of the embodiment of the invention disclosed in Fig. 1 may advantageously be employed in the embodiment of Fig. 3, and vice versa. For example the coating means 23 of Fig. 1 may be employed to obtain a high resistivity and thermoplastic coating for the recording medium of Fig. 3 while the powder-applying means 55 and the heating means 58 of Fig. 3 may be employed with the recording means 1619 of Fig. 1.

There have been described herein improved apparatus and improved operating methods for electrically recording information patterns upon a dielectric body. These 4 are by way of illustration and not by way of limitation nail.

of the invention. The limits of the invention are defined solely in the appended claims.

What is claimed is:

1. Apparatus for electrically recording signals comprising, in combination, radioactive material, a container enclosing the radioactive material and provided with a discharge conduit through which ionic particles generated from the discharge about the radioactive material are emitted, control means associated with said conduit for varying the volume of ions discharged from the open end of the conduit, a grounded plate electrode positioned to receive the ions discharged from the conduit, a recording member having a dielectric coated surface, means for feeding the recording member between the plate electrode and the discharge conduit of the container and so as to present the dielectric coated surface of the member to the ions discharged from the conduit, means for forming a cloud of inking powder, means for passing the recording member thus charged through said cloud of inking powder to cause the inking powder to cling to the charge pattern on the member, and means for rendering the charged areas of the recording member permanently visible thereon.

2. Apparatus as defined in claim 1 wherein said container is formed of conductive material and means are provided for electrically charging the container, to exert a force on said ions.

3. Apparatus as defined in claim 2 wherein said control means comprises an electrode positioned to exert a force, when charged, on said ions, and means are provided for selectively charging said electrode to a potential opposite in sign to that of said container.

4. In recording apparatus, the combination of a radioactive source emitting particles in random direction therefrom and operative to provide electrically charged particles; means directing said electrically charged particles into a unidirectional stream, electrode means for selectively controlling said stream; and a recording medium capable of retaining an electrostatic charge, said medium positioned to receive said stream and to be charged thereby.

5. In electrostatic recording apparatus the combination of a source of electrically charged particles generated by radioactive material, a displaceable recording medium capable of retaining electrostatic charges, means for directing at least a portion of said electrically charged particles for impingement on said medium as a fine stream normal thereto, means for modulating said stream to control the charging of said medium, thereby to produce in conjunction with displacement of the medium a pattern of discrete charged areas of the medium, and means for controlling the operation of said modulating means to determine the nature of said pattern.

6. In recording apparatus the combination of a source of electrically charged particles generated by radioactive material, conductive container means therefor having an orifice, said container means adapted when electrically charged to direct certain of said particles into a unidirectional stream issuing from said orifice, means for electrically charging said conductive means, a dielectric recording medium capable of retaining an electrostatic charge positioned to receive said stream and to be charged thereby over a limited area, means for selectively controlling the reception of said stream by said medium, means for displacing the medium to provide for the reception of said stream at difilerent areas of the medium, and means for rendering visible the areas of the medium charged by said stream.

7. The combination defined in claim 6 wherein said means selectively controlling the reception of said stream by said medium comprises electrode means exerting, when charged, a controlling force on the particles of said stream, and charging means therefor controllable in accordance with the pattern of charged areas to be produced on said medium.

8. In electrostatic recording apparatus the combination of a source of electrically charged particles generated by radioactive material, a portion of said electrically charged particles having an electrostatic charge of given sign, conductive means substantially surrounding said source having an orifice therein, means for producing a charge of said sign on said conductive means thereby through electrostatic forces to produce a tendency for electrically charged particles having a charge of said sign to issue from said orifice, a displaceable medium having a chargeretentive surface positioned to receive electrically charged particles issuing from said orifice, and electrostatically operable means for controlling the tendency of electrically charged particles of said sign to issue from said orifice.

References Cited in the file of this patent UNITED STATES PATENTS 1,590,452 Sparkes June 29, 1926 1,806,375 Tiedman May 19, 1926 2,143,214 Selenyi Jan. 10, 1939 2,200,741 Grey May 14, 1940 2,221,776 Carlson Nov. 19, 1940 2,701,764 Carlson Feb. 8, 1955 2,747,133 Weimer May 22, 1956 

